= SQL Module

== Introduction

The SQL module is composed of two parts: a generic SQL front-end
(rlm_sql), and a series of database-dependent back-end drivers,
(rlm_sql_mysql, rlm_sql_postgresql, etc.)

In order to build the drivers, you MUST ALSO install the development
versions of the database. That is, you must have the appropriate header
files and client libraries for (say) MySQL. The rlm_sql_mysql driver is
NOT a complete MySQL client implementation. Instead, it is a small
"shim" between the FreeRADIUS rlm_sql module, and the MySQL client
libraries.

In general, the SQL schemas mirror the layout of the "users" file. So
for configuring check items and reply items, see `man 5 users`, and the
examples in the users file.


== Schema and usage

The schemas are available in `raddb/sql/*`, where is the name of the
database (mysql, postgresql, etc.)

The SQL module employs two sets of check and reply item tables for
processing in the authorization stage: One set of tables (radcheck and
radreply) are specific to a single user. The other set of tables
(radgroupcheck and radgroupreply) is used to apply check and reply items
to users that are members of a certain SQL group. The usergroup table
provides the list of groups each user is a member of along with a
priority field to control the order in which groups are processed.

When a request comes into the server and is processed by the SQL module, first
user attribute processing is performed:

. The radcheck table is searched for any "check" attributes specific to the
user
. If check attributes are found for the user, and they match the request:
.. "Control" attributes from the radcheck table for this user are added to the control list, then
.. "Reply" attributes from the radreply table for this user are added to the reply

Next, group attribute processing is performed if any of the following
conditions are met:

- The user IS NOT found in radcheck
- The user IS found in radcheck, but the check items DO NOT match
- The user IS found in radcheck, the check items DO match AND
Fall-Through is set in the radreply table
- The user IS found in radcheck, the check items DO match AND the
read_groups configuration item for the sql module is set to `yes`

If groups are to be processed for this user, the first thing that is
done is the list of groups this user is a member of is pulled from the
radusergroup table, ordered by the priority field. The priority field of the
radusergroup table provides control over the order in which groups are
processed, emulating the ordering in the layout of the users file.

Considering the groups in order of priority:

. The radgroupcheck table is searched for any check attributes specific to the group
. If check attributes are found for the group, and they match the request:
.. The control attributes from the radgroupcheck table for this group are added to the control list
.. The reply attributes from the radgroupreply table for this group are
added to the reply

Processing continues to the next group if any of the following conditions are met:

- There was not a match for the last group’s check items OR
- Fall-Through was set in the last group’s reply items

The above is exactly the same as in the `users` file.

=== Example with groups

For any fairly complex setup, it is likely that most of the actual
processing will be done using groups. In these cases, the user entries
in radcheck and radreply will be of limited use except for things like
setting user-specific attributes such as the user’s password. So, one
might have the following setup:

.radcheck table
|===
|UserName | Attribute          | Op | Value

|joeuser  | Password.Cleartext | := | somepassword
|===

.radreply table
|===
|UserName | Attribute          | Op | Value

|joeuser  | Fall-Through       | =  | Yes
|===

.radusergroup table
|===
|UserName | GroupName    | Priority

|joeuser  | WLANgroup    | 1   (Applied first)
|joeuser  | MeteredGroup | 2
|===

.radgroupcheck table
|===
|GroupName    | Attribute          | Op | Value

|Check items for various connection scenarios... | | |
|MeteredGroup | Simultaneous-Use   | := | 1
|===

.radgroupreply table
|===
|GroupName    | Attribute          | Op | Value

|Reply items for the groups... | | |
|WLANgroup    | Tunnel-Type             | := | VLAN
|WLANgroup    | Tunnel-Medium-Type      | := | IEEE-802
|WLANgroup    | Tunnel-Private-Group-ID | := | 20
|MeteredGroup | Filter-Id          | := | 123
|===


== What NOT to do!

One of the fields of the SQL schema is named "op". This is for the "operator"
used when evaluating the attributes, e.g.

[source,config]
----
Framed-IP-Address     :=      1.2.3.4
^ ATTRIBUTE ^       ^ OP ^   ^ VALUE ^
----

If you want the server to be completely misconfigured, and to never do
what you want, leave the `op' field blank. If you want to be rudely told
to RTFM, then post questions on the mailing list, asking

_Why doesn’t my SQL configuration work when I leave the `op` field
empty?_

The short answer is that with the op field empty, the server does not
know what you want it to do with the attribute.

  * Is it a check item that should be compared against the request?
  * Should it be added to the control or reply list?

Without the operator, the server simply doesn’t know, so always put a
value in the field. The value is the string form of the operator: "=",
">=", etc. See below for more details.


== Authentication versus Authorization

Many people ask if they can "authenticate" users to their SQL
database. The answer to this question is "You’re asking the wrong
question."

An SQL database stores information. An SQL database is NOT an
authentication server. The ONLY users who should be able to authenticate
themselves to the database are the people who administer it. Most
administrators do NOT want every user to be able to access the database,
which means that most users will not be able to "authenticate"
themselves to the database.

Instead, the users will have their authorization information (name,
password, configuration) stored in the database's tables. The
configuration files for FreeRADIUS contain a username and password used
to authenticate FreeRADIUS to the SQL server. (See raddb/sql.conf). Once
the FreeRADIUS authentication server is connected to the SQL database
server, then FreeRADIUS can pull user names and passwords out of the
database, and use that information to perform the authentication.


== Operators

The list of operators is given here.

=== =

e.g.: `Attribute = Value`

Not allowed as a check item for RADIUS protocol attributes.  It is
allowed for server configuration attributes (Auth-Type, etc), and sets
the value of an attribute, only if there is no other item of the
same attribute.

As a reply item, it means "add the item to the reply list, but
only if there is no other item of the same attribute."

=== :=

e.g: `Attribute := Value`

Always matches as a check item, and replaces in the
configuration items any attribute of the same name.  If no
attribute of that name appears in the request, then this
attribute is added.

As a reply item, it has an identical meaning, but for the
reply items, instead of the request items.

=== ==

e.g: `Attribute == Value`

As a check item, it matches if the named attribute is present
in the request, AND has the given value.

Not allowed as a reply item.

=== +=

e.g: `Attribute += Value`

Always matches as a check item, and adds the current attribute
with value to the list of configuration items.

As a reply item, it has an identical meaning, but the
attribute is added to the reply items.

=== !=

e.g: `Attribute != Value`

As a check item, matches if the given attribute is in the
request, AND does not have the given value.

Not allowed as a reply item.

=== >

e.g: `Attribute > Value`

As a check item, it matches if the request contains an
attribute with a value greater than the one given.

Not allowed as a reply item.

=== >=

e.g: `Attribute >= Value`

As a check item, it matches if the request contains an
attribute with a value greater than, or equal to the one
given.

Not allowed as a reply item.

=== <

e.g: `Attribute < Value`

As a check item, it matches if the request contains an
attribute with a value less than the one given.

Not allowed as a reply item.

=== \<=

e.g: `Attribute \<= Value`

As a check item, it matches if the request contains an
attribute with a value less than, or equal to the one given.

Not allowed as a reply item.

=== =~

e.g: `Attribute =~ Expression`

As a check item, it matches if the request contains an
attribute which matches the given regular expression.  This
operator may only be applied to string attributes.

Not allowed as a reply item.

=== !~

e.g: `Attribute !~ Expression`

As a check item, it matches if the request contains an
attribute which does not match the given regular expression.
This operator may only be applied to string attributes.

Not allowed as a reply item.

=== =*

e.g: `Attribute =* Value`

As a check item, it matches if the request contains the named
attribute, no matter what the value is.

Not allowed as a reply item.

=== !*

e.g: `Attribute !* Value`

As a check item, it matches if the request does not contain
the named attribute, no matter what the value is.

Not allowed as a reply item.


== Module instances

As with other modules, multiple instances of the rlm_sql module can
be defined and used wherever you like.

The default module configuration files for the different database types,
contain one instance without a name like so:

[source,config]
----
sql {
    ...
}
----

You can create multiple named instances like so:

[source,config]
----
sql sql_instance1 {
    ...
}

sql sql_instance2 {
    ...
}
----

And then you can use a specific instance in radiusd.conf, like so:

[source,config]
----
recv Access-Request {
    ...
    sql_instance1
    ...
}

process Accounting-Request {
    ...
    sql_instance1
    sql_instance2
    ...
}
----
